1. Field of the Invention
This invention relates to a continuous underground trench excavating method and an excavator therefor to form a continuous underground wall.
2. Description of the Related Art
TRD (Trench-cutting Re-mixing Deep Wall) method is known as creation method for continuous underground wall. In a case of creating a water stop wall or an earth retaining wall under the ground deeply, it is extremely important to control whether or not an excavating machine reaches an impermeable layer or a supporting foundation.
Generally, as boring data by drilling survey are limited to a certain work site where the survey is executed actually, however, in case that there exist lot of changes on the condition of layer of earth, it depends on erroneous assumption whether or not a lower end of an excavating machine reaches an impermeable layer or a supporting foundation. Accordingly, as it is, excessive excavation has to be carried out up to a depth where the lower end thereof could reach the impermeable layer absolutely even if the changes exist.
As a result, it gives rise to not only more costly execution but also unnecessary delay in construction schedule. If things come to the worst, completion comes to miss the fixed deadline.
According to a method of improving the ground as described in Japanese Patent Application publication No. Hei 11-280055, a stirring stick with a stirring wing mounted on the end thereof is inserted vertically into the ground with mixing action up to a predetermined depth and then the stick is lifted up while an improving material is poured from the end and the mixing action of the stick is carried out, thereby an improved ground is formed. In this case, when there exist lot of changes on the condition of layer of earth, it also depends on the above erroneous assumption since the boring data do not represent all the ground to be excavated.